How much resolution can I expect to get copying color slides and film with a 26 MP camera?

[Overrank]

My personal experience scanning negative/slide film back in the 90's indicated that grain could be discerned in ISO (then ASA) 100 film at about 4000dpi, thus I concluded that 16mpx was about equivalent when digital cameras started to be introduced.

That would yield about 24mp from a 35mm frame rather than 16.

It’s about 21.4MP

Yes, that's more precise, but 24mp cameras are easier to find.

But 4000dpi scanners are also pretty common

but I’ve found it to be roughly equivalent to a 45MP camera when you account for all the losses in the system when using a camera (based on measurement of high contrast targets ). The real problem is the source material (image) rather than film resolution issues.

That last sentence is the key part. With my own slides that were shot using mainstream gear under a wide range of conditions, I get virtually nothing of use beyond 24mp.

I do have a way to photograph a small section of a 35mm slide at the equivalent resolution of a 130mp camera with no AA filter. I think I tried it once, but maybe it's time to try again.

Some films ( for example CMS-20 ) can easily out resolve consumer scanners (and most camera/lens combos). But they’re very taxing to shoot, and at 12-25 ISO tripods are a must.

 

[Overrank]

My personal experience scanning negative/slide film back in the 90's indicated that grain could be discerned in ISO (then ASA) 100 film at about 4000dpi, thus I concluded that 16mpx was about equivalent when digital cameras started to be introduced.

That would yield about 24mp from a 35mm frame rather than 16.

But the film grain was (easily) DISCERNABLE @ 4000dpi ... which means it was BEYOND the actual film resolution, (which I concluded was between 3000 & 4000dpi -- thus about 16mpx).

The image in black and white film is made up of silver crystals. The actual size of these crystals in black and white film is around 1 micron ( see for example Colour Granularity and Graininess, D Zwick, The Journal of Photographic Science, 11 (5), 1953 - of course that’s prior to T-Grain).

The grain that you can see in black and white photographs are not the actual crystals themselves, they’re too small, instead it’s the three dimensional optical / mental clumping of these silver particles (Zwick again) not the particles themselves.

How grain looks depends on how you observe it - film scanner looks different to optical printing looks different to drum scanner, so I’m not sure that you can make any inference of the film resolution based on visibility or not of grain.

Thats not including B&W films which are pretty grainless (CMS-20) or colour films, which have soft edged dye clouds, rather than hard edged crystals.

ASA 25 was somewhat higher at about (between 4 & 5000dpi (aka 24mpx) ...

That would yield about 36mp from a 35mm frame rather than 24.

It appears the manufacturers knew that also since the mpx "wars" seemed to stop at 24mpx, (until recently).

 

[Scott_Eaton]

Ask any commercial photog in the late 90s or early 2000's what looked better....a 4000dpi scan from 35mm or a 2000dpi scan from medium format. The 2000dpi scan from MF was like a kick in the head compared to the 35mm scan at higher rez.

So, anybody claiming 4000dpi scans from film are perfectly fine and recording absolute information discounts the advantages of MF. Can't have it both ways. Beyond 2000dpi conventional films start to fall apart. Color neg falls apart the fastest because of the sloppy way the dye couplers produced grain clouds. The sightest under exposure in color neg starts to degrade it's resolution quickly.

Finer grain film doesn't account for more resolution. It produces finer resolving fringe contrast which MAY result in more absolute information.

Raise your hand if you'v worked on a hign end drum scanner. My Howtek started to produce obvious grain in slow speed slide films at 2000-2500 dpi. The only reason commercial pros wanted higher resolution scans is back then interpolation software wasn't as good as taking higher res scan and people still read magazines. If you can't resolve sharp grain in low speed slide films at 2000di you need to put the Epson flatbed away and try a dSLR scan with a good lens.

Film also doesn't resolve resolution in s linear fashion. Reversal film was the most consistent...up until highlights turned to clear film stain and didn't record information. Some films, notoriously Kodak would die quickly as certain colors / dye became saturated. The reason Kodachrome was so revered is it maintained consistent resolution within a printable range, then died quickly due to it's lack of dynamic range. The fact it resolved very well within the most important ranges of conventional printable tone ranges was all that mattered. Was what gave it it's 'look'. Newer dye coupled E-6 had other compromises. Still preferred Kodachrome 25 over Velvia.

Optically printed 35mm was horrendously difficult to get max information. Good film scanners did it better. Going back and dSLR scanning some of my older film the thing that catches my attentin is how crappy our optics were. Nikon and especially Canon must have employed Coke bottling engineers in their optic divisions. APS-C lenses especially have made massive optical improvements.

 

[a_c_skinner]

My best slides come out comparable with my D200 - 10Mpix. Roughly. Kodachrome 64 shows no grain, K200 shows obvious grain. I've had good outcomes with Topaz Photo AI and I think if I put more effort into this I could improve on what I get by using selective sharpening and noise reduction.

Many of my slides are not as sharp as I'd have liked. Lenses have got better, focussing more precise (mine are all MF). The one thing I'd say is that you need to be ruthless and simply discard a lot of them.

There are some surprises. This is two slides, probably K64, that happened to stitch together. Tryfan, the Glyders and Y Garn, North Wales. It is on my lounge wall about 30" wide on canvas. I think it needs the help the canvas gives it!

https://flic.kr/p/2oMAtMv

if you want to look at the big file.

--
Andrew Skinner

 

[Cultius Ponc]

Hmm. My old Minolta Dimage Scan Elite 5400 produces approx 40.8Mp image files. 5,232 x 7,800 pixels. So a little larger than the '6Mp' figure some have suggested. A high quality colour print from such a scan is indistinguishable from a colour print from the original slide. Yet a print from a copy using a 12Mp cam, 60mm macro lens and slide copying attachment, was noticeably inferior. So I wouldn't put too much faith in that 6Mp claim. Slides shot on 100 ISO film are as sharp and well defined as images shot on my 24Mp cam. The digital cam has greater DR, for sure, and of course much more 'latitude' in the RAW file, but the film still produces very high resolution' images.

 

[jonikon]

Many thanks to all who responded to my question with a wealth of information. (Much more than I expected, actually). Now at least I know there isn't any point in saving the digital copies at more than 12MP at best. Although I still have much to learn about coping slides and negatives the information provided here gives me an idea of what to (and not to), expect from the end product.

 

[PhotoTeach2]

Many thanks to all who responded to my question with a wealth of information. (Much more than I expected, actually). Now at least I know there isn't any point in saving the digital copies at more than 12MP at best. Although I still have much to learn about coping slides and negatives the information provided here gives me an idea of what to (and not to), expect from the end product.

How did you get to the conclusion of (only) 12mpx ???

The number is around 16mpx for ISO-100 equivalent, but closer to the 20-26mpx for lower-ISO equivalent films/slides (aka Kodacrome or Ektar 25) ...

While I agree that 12mpx is possibly sufficient for your (immediate) intentions, you may want higher mpx in the future so I always suggest saving at the highest mpx.

 

[John Crowe]

I equate Kodachrome 25 and Velvia 50 to 20-24MP FF. My 50MP FF does at least what 6x6 Velvia used to do, and when I stitch, it easily gets to 4x5 Velvia.

Several years ago I digitized my Kodachrome 25, 64, Ektar 25, Velvia 50, and Ektachrome 100 VS with my 21MP FF camera. The results were far superior to my 2800 dpi film scans, and I was quite pleased with them. I have since digitized many with my 50MP camera and the results are significantly better.

It is amazing how much detail can be pulled out of shadows that I never knew was there. The overall exposure balance you can achieve in post processing is a huge bonus. Oddly enough I have found that digitizing 4x5 film with a camera can provide deeper more saturated colours than the camera itself does.

I have made 16x20 LightJet prints from camera digitized 35mm film that do not look out of place beside prints from my 21 and 50MP camera.

 

[bjn70]

Hmm. My old Minolta Dimage Scan Elite 5400 produces approx 40.8Mp image files. 5,232 x 7,800 pixels. So a little larger than the '6Mp' figure some have suggested. A high quality colour print from such a scan is indistinguishable from a colour print from the original slide. Yet a print from a copy using a 12Mp cam, 60mm macro lens and slide copying attachment, was noticeably inferior. So I wouldn't put too much faith in that 6Mp claim. Slides shot on 100 ISO film are as sharp and well defined as images shot on my 24Mp cam. The digital cam has greater DR, for sure, and of course much more 'latitude' in the RAW file, but the film still produces very high resolution' images.

When I say 6MP it is based on looking at photos taken on film and comparing with photos taken with my D70S. I think if you take a negative that has 6MP of resolution and you try to copy it with a digital camera,, you need to use a higher resolution sensor to be sure of capturing the detail.

I can't dispute the people who say they got much higher resolution from other types of film. I frequently used K64 and never thought I got all that much detail from it.

Here is a photo I digitized a few months ago. The original photo was taken about 50 years ago likely on Tri-X. I digitized it with a 24mp APS-C sensor and a Tamron 90mm macro lens. I think the 24mp sensor did a pretty good job of capturing the detail in this negative.





Here is a photo digitized from a transparency. The original photo was taken in 1993, probably K64 film. It was digitized about 5 years ago using a 24MP APS-C sensor using a Nikon 105mm f4 macro lens.

 

[Overrank]

Many thanks to all who responded to my question with a wealth of information. (Much more than I expected, actually). Now at least I know there isn't any point in saving the digital copies at more than 12MP at best. Although I still have much to learn about coping slides and negatives the information provided here gives me an idea of what to (and not to), expect from the end product.

How did you get to the conclusion of (only) 12mpx ???

Many people on here ask questions to confirm their own opinion ….

(it’s also highly subjective to the source material, what was the original lens, was it in focus, was the scene lit correctly etc)

The number is around 16mpx for ISO-100 equivalent, but closer to the 20-26mpx for lower-ISO equivalent films/slides (aka Kodacrome or Ektar 25) ...

While I agree that 12mpx is possibly sufficient for your (immediate) intentions, you may want higher mpx in the future so I always suggest saving at the highest mpx.

 

[a_c_skinner]

I don't think that is true. Every stage in a process contributes to the final result and better resolution at any stage will improve the final result. At least in theory. Going up to 100Mpix won't make a huge difference over 40Mpix but lower down the scale you will see more. It isn't as simple as 10Mpix in the slide means 10Mpix is enough to get a decent copy.

 

[tbcass]

You can still read that the dynamic range of color negative film exceeds digital I always found that laughable even in the early days of film scanning and early raw digital capture.

I recently did some research online to answer a DR question in another post. From the available information I found that the best color negative film has at most 14 stops of DR and slide film has 9 stops. Sensors these days can have 14 stops or more. The limiting factor is the way the photo is viewed. The typical JPEG image has only 8 stops and prints have even less.

--
Tom

 

[tbcass]

I believe my 26MP camera with a good macro lens can out-resolve the detail in my old color slides and color negatives. My question is what would be the comparable resolution of the resulting image in terms of MP's? Someone told me not to expect any better image quality than a 6MP digital camera. I get that the weak link here is the slide or negative, but 6MP of useable resolution seems a bit low to me. Hopefully someone must have figured this out by now.

I’ve recently posted in the film forum some example digitisations of a slide made with different resolution digital cameras - https://www.dpreview.com/forums/thread/4741864 These are with modern colour slide film shot recently

There are details on the slide that needed a 45MP camera (or a 4000dpi scanner) to resolve. You will lose some resolution through the camera/lens arrangement - I’ve found on tests that I only get around 60% of the linear resolution. As with digital cameras there’s a sweet spot of usable information, and more than that isn’t required in most cases - 24 MP seems a resonance compromise.

Using the gauges to judge detail is seems that the film resolves slightly more than 24mp and less than 45. If I was to guess I would estimate around 30MP.

 

[bastibe]

There's a difference between the resolution necessary to resolve the photographic detail on the one hand, and resolving the film grain, on the other.

6 MP is plenty for the photo. Perhaps add a few MP to account for capture loss (demosaicing, noise, lens...). The film didn't capture much more information than that.

But to some, the rendition of grain is part of the aesthetic. If you want to capture that, you'll need much more resolution.

From my own scanning, I'd say 24 MP is still plenty for 35mm film.

 

[Guy Parsons]

Many thanks to all who responded to my question with a wealth of information. (Much more than I expected, actually). Now at least I know there isn't any point in saving the digital copies at more than 12MP at best. Although I still have much to learn about coping slides and negatives the information provided here gives me an idea of what to (and not to), expect from the end product.

How did you get to the conclusion of (only) 12mpx ???

Just for interest, Olympus long told us that about 10MP to 12MP does as well as 35mm film.

In my own digital camera adventures starting at 3MP and growing over the years I found that when I reached 8MP I was as happy as I was with film for a result. But of course soon finding the hard printing size limit, unlike film where the print size can go on forever and in larger sizes the increasing grain size nicely hides the fact that there's no fine detail.

Using a camera to digitise I didn't quite get what I wanted with a 12MP camera but got all there was to get from 35mm film using my 16MP Olympus camera. I compared fine detail to what I could shoot through a lab microscope at ever higher magnifications and there was definitely no more details to be found by going past my 16MP camera.

The number is around 16mpx for ISO-100 equivalent, but closer to the 20-26mpx for lower-ISO equivalent films/slides (aka Kodacrome or Ektar 25) ...

So in my case 16MP suited my years of Fuji Sensia 100 shot at ASA 125 using a quality Nikon SLR. My KowaSix 6x6 and Bronica 6x4.5 slides however did really need more MP but 16MP was still good enough for my purposes. My early days B&W efforts on slow film also could do with more than 16MP, but why? I was never going to print bigger than maybe A3 anyway, so the extra MP lust not needed.

While I agree that 12mpx is possibly sufficient for your (immediate) intentions, you may want higher mpx in the future so I always suggest saving at the highest mpx.

Use whatever highest MP camera you own with a good macro lens and then decide from the result what MP size to keep the images long term. If I had a 60MP camera I'd probably use that .... and then resize (or crop) back to 20MP or something like that.

Just for fun, my usual copy rig....


Overkill construction simply because I have a mill-drill and wanted to play with it.

Olympus E-PL5 (16MP) with 60mm macro lens, master flash on body controls slave flash to illuminate the slide, TTL method works fine. Touch screen AF and shoot used. A cheap Velbon macro rail with an added adapter plate holds the camera. Weak light (not shown) aimed at back of slide to help AF.

Slide and film holders from an old Microtek SCSI 4000dpi film scanner (stopped with that as was too slow to use).

Flash now moved back a few more inches as that setup was too close for very thin slides.

Frame nearest lens also holds 6x6 or 35mm slides using push-pull two frame slide holders off an old projector.

 

[KENTGA]

Thanks for asking the question. I look forward to the replies. I'm in the same boat.

Kent

 

[PhotoTeach2]

I don't think that is true. Every stage in a process contributes to the final result and better resolution at any stage will improve the final result.

More accurate is that any (single) stage in the process can ruin the final result.

It is limited by the weakest-link.

At least in theory. Going up to 100Mpix won't make a huge difference over 40Mpix but lower down the scale you will see more. It isn't as simple as 10Mpix in the slide means 10Mpix is enough to get a decent copy.

The point is that 16mpx (or 20-25 from ASA/ISO-25) is the most sharpness possible from (FF) 35mm.

Either 40 or 100mpx won't see any improvement, (unless cropping).

But other errors (aka focus/shake/exposure), can reduce that, to the weakest-link.

 

[Guy Parsons]

I don't think that is true. Every stage in a process contributes to the final result and better resolution at any stage will improve the final result.

More accurate is that any (single) stage in the process can ruin the final result.

It is limited by the weakest-link.

At least in theory. Going up to 100Mpix won't make a huge difference over 40Mpix but lower down the scale you will see more. It isn't as simple as 10Mpix in the slide means 10Mpix is enough to get a decent copy.

The point is that 16mpx (or 20-25 from ASA/ISO-25) is the most sharpness possible from (FF) 35mm.

That holds true for me with my Fuji Sensia 100 slides shot at 125, my Micro Four Thirds gear at 16MP does get all there is to get, above that it's simply grain clumps being resolved.

Either 40 or 100mpx won't see any improvement, (unless cropping).

But other errors (aka focus/shake/exposure), can reduce that, to the weakest-link.

I found that using TTL flash to back (diffused) illuminate the slide removes the shake/shock issues, AF focus and shoot by touch screen on a suitable contrasty part of the slide worked fine, no misses. A good macro lens and the usual auto metering in A mode with the f/2.8 macro lens set to f/5.6 to help give a better depth of field for wonky slides works well for me.

Raw files of course and adjust for any brightness issues and gently expand the dynamic range in post works well. It's surprising what can be dragged out of murky shadowy slides without the result looking like horrible HDR efforts.

I also messed about with slide and film copy using an Epson V700 flat bed scanner. That one has two lens systems and a grand difference in results depending on which lens is used. A while since I did this but here's a comparison between the two lenses interpolated to match the look....


Left using higher res lens.

Whole image from an old B&W film shot taken in 1963 or 1964, my old 1951 Mercedes Benz 170V (designed in 1936 which is obvious). Bought in 1962(?) sold it in 1964....



Though when digitising old slides it is often that I see shake and minor misfocus issues in the slide that were never obvious when projected on a screen. Our ability and habit to pixel peep finds all errors.